P2P protocol version 2, adding SUCCESS-PLUS and ALREADY-HAVE-PLUS

Client side support for SUCCESS-PLUS and ALREADY-HAVE-PLUS
is complete, when a PUT stores to additional repositories
than the expected on, the location log is updated with the
additional UUIDs that contain the content.

Started implementing PUT fanout to multiple remotes for clusters.
It is untested, and I fear fencepost errors in the relative
offset calculations. And it is missing proxying for the protocol
after DATA.

Types/Transfer.hs

@@ -89,6 +89,12 @@ instance Observable (Maybe a) where
 	observeBool Nothing = False
 	observeFailure = Nothing
 
+instance Observable (Either e (Maybe a)) where
+	observeBool (Left _) = False
+	observeBool (Right Nothing) = False
+	observeBool (Right (Just _)) = True
+	observeFailure = Right Nothing
+
 class Transferrable t where
 	descTransfrerrable :: t -> Maybe String